Devices with movable components may experience degradation, efficiency losses, and shortened service life due to component wear. For example, engine components, cutting tools, and devices configured for converting energy, such as hydraulic pumps and hydraulic motors, often include gears, bearings, and other movable components which translate and/or rotate with respect to a countersurface. After many operation cycles, friction between such movable components and the countersurface may cause degradation, i.e., wear, of the movable component. Such friction and wear may contribute to one or more performance problems of the devices.
For example, during a break-in period of hydraulic devices such as vane pumps, axial piston pumps, and orbital motors, increased friction between movable components often limits operating pressures, and in turn negatively impacts power density of the devices. To compensate for such pressure limitations, existing devices often require sulfur and/or phosphorus hydraulic fluid additives to generate protective sulfites and/or phosphates on surfaces of the devices.
Moreover, increased friction and wear often increases start-up torque requirements for devices. In particular, increased friction and wear may further decrease an already-low start-up mechanical efficiency of a device. For example, existing devices may exhibit low start-up mechanical efficiency and are often oversized above a nominal torque output to meet expected performance requirements. Increased friction further aggravates such low start-up efficiency and often requires a comparatively larger device, with accompanying larger energy consumption, to produce a given torque output.
Additionally, increased friction, and the accompanying wear and degradation at various mechanical interfaces, also decreases the mechanical efficiency of existing devices during non-start-up operating conditions. For example, increased friction may contribute to ring burn, i.e., excessive wear and gouging of a ring of a vane pump, which negatively impacts the mechanical efficiency and service life of existing vane pumps.
Further, increased friction may impose maximum operating speed and pressure limitations on existing devices operated with non-petroleum-based hydraulic fluids. Since non-petroleum-based hydraulic fluids typically provide decreased lubrication as compared to petroleum-based hydraulic fluids, any increased friction between components limits the operating speed and pressure of existing devices operated with non-petroleum-based hydraulic fluids.